This invention relates to the field of minesweeping, and more particularly to an improved cutter device for severing mine mooring cables engaged by a sweep wire.
It has been the practice to provide the sweep wire of towed minesweeping gear with one or more explosively actuated cutters for severing the mine mooring cables. The cutters typically comprise a body mounted on the sweep wire and having a jaw or hook which is engaged by a mooring cable as it slides along the towed sweep wire. The body is usually provided with a vane that assumes a horizontal position aft of the sweep wire during tow and positions the body with the jaw or hook ready to be engaged by a mooring cable. Upon such engagement a firing sequence is initiated to propel a chisel through the cable to sever it, usually against an anvil.
U.S. Pat. No. 2,422,506 provides an example of a minesweeping cutter wherein the firing mechanism is a spring and lever apparatus and the cable is backed by an anvil during cutting. U.S. Pat. No. 3,760,674 utilizes a spring driven plunger and hydraulic column means in the firing mechanism, and an anvil. U.S. Pat. No. 4,074,650 discloses a firing mechanism wherein the chisel is engaged by the mooring cable and displaced with its barrel to shear a pin and allow a spring to drive the barrel rearwardly so that a confined slug of seawater causes a piston carried firing pin to actuate an explosive cartridge. In that device the chisel is intended to be driven through the mooring cable without benefit of backing by an anvil, or the like. While the lack of an anvil is desirable from the standpoint of cost and simplicity, the configuration taught in the mentioned patent has the shortcoming of not developing an impact velocity in the chisel before contact with the cable, and hence is limited in severing capability.
The use of springs, levers, and the like, in the firing mechanism not only reduces reliability and adds to initial cost, but also increases the time and effort that must be expended in disassembly, cleaning, lubricating and reassembly after streaming. Moreover, existing cutter devices incorporate complex means of attachment to the sweep wire, often requiring the use of both hands, thereby adding to personnel risk in heavy weather.